1. Field of the Invention
The present invention relates generally to semiconductor devices, and more particularly, to a semiconductor memory device whose word configuration can be changed after molding.
2. Description of the Background Art
In semiconductor memory devices such as SRAM, the word configuration of multi-bit memories are changed by means of aluminum master slice approach or bonding option. The aluminum master slice approach requires change of aluminum masks, resulting in high cost, while the masks do not have to be changed by bonding option.
FIG. 11 is a plan view showing an example of a conventional semiconductor memory device whose word configuration can be changed by bonding option. As shown in FIG. 11, a plurality of pads 2 to 6 are formed on a semiconductor chip 1. Pad 2 for setting a word configuration is formed next to pad 3 for power supply, and another pad 4 for setting a word configuration is formed next to pad 5 for grounding.
The following Table 1 represents word configuration set based on the states of pads 2 and 4, MODE 1 and MODE 2.
TABLE 1 ______________________________________ Word Configuration .times.8 .times.4 .times.1 ______________________________________ MODE 1 HiZ HiZ H MODE 2 HiZ L HiZ ______________________________________
When not bonded, both pads 2 and 4 attain a high impedance state (HiZ) as in Table 1, and therefore .times.8 configuration is selected. When pad 2 is not bonded and pad 4 is bonded with pad 5, pad 2 attains a high impedance state, pad 4 attains an L (logical low) level (ground voltage GND) state, and therefore the word configuration is changed to .times.4 configuration. When pad 2 and pad 3 are bonded and pad 4 is not bonded, pad 2 attains an H (logical high) level (power supply voltage VCC) state as in Table 1, pad 4 attains a high impedance state, and therefore the word configuration is changed to .times.1 configuration.
Such bonding option allows the word configuration to be changed at the time of wire bonding, the wafer test can be conducted with a multi-bit configuration (.times.8 configuration herein). Therefore, time required for such test is shorter than the aluminum master slice approach, and cost for the test is advantageously lower.
The bonding option, however, requires additional pads 2 and 4 for setting the word configuration, and the area penalty becomes large. Furthermore, the word configuration set at the time of wire bonding can not be changed after molding.